Color photography



Ap 15, 1952 J. H- cooT'E ETAL 2,592,864

COLOR PHOTOGRAPHY I Filed Dec. 16, 1947 EMULSION CONTAINING YELLOW COLOR FORMER AND FUGITIVE YELLOW OYESTUFF BASE STARTING MATERIAL.

MAGENTA COLOR FORMER AND FUGITIVE YELLOW DYESTUFF.

EMULSION commmc PRINTING LIh-T I. .II

PRINTING LIGHT COLOR AND ILERRICYANIDE L E 7 TMEIYI-E BLEACH.

FINISHED IMAGES.

ttorneya Patented Apr. 15, 1952 COLOR PHOTOGRAPHY Jack Howard Coote and Keith Milton Hornsby, London, England, assignors to Dufay-Chromex Limited, London, England, a British company Application December 16, 1947, Serial No. 792,094

In Great Britain December 9, 1946 Section 1, Public Law 690, August 8, 1946 Patent expires December 9, 1966 8 Claims. (01. 95-2) This invention relates to the production of coloured photographic images and more particularly to the production of motion pictures in colour.

In application Serial No. 712,245, filed November 26, 1946, now Patent No. 2,509,232 of May 30, 1950, one of us, J. H. Coote, has described a process for the production of a multi-colour photographic image which comprises coating a photographic base material with a first composition containing a silver halide and a substantially non-mobile colour former-dispersed in a photographic emulsion colloid, printing from a first colour separation record, coating the printed emulsion with a second composition containing a silver halideand a second substantially non-mobile colour former dispersed in the same photographic emulsion colloid as that of said first composition so as to produce, on drying, a second silver halide emulsion layer directly superposed on said printed emulsion, printing from the second colour separation record of said set, simultaneously developing the successively-produced latent images and coupling with a colour developer.

When this process is applied to the production of a three-colour photographic image three coating and printing stages are involved, each We have now found that it is possible to proceed in a different manner from that of the said application by first producing a base material carrying two emulsion layers, printing the layer more remote from the base from the appropriate colour separation negative, printing the layer adjoining the base through the base from the appropriate colour separation reverse negative, followed by simultaneously developing the successively produced latent images and coupling as in the process of the parent application.

Accordingly, the process for the production of a multicolour photographic image in accordance with the present invention comprises printing the outer emulsion layer of a photographic material comprising a transparent base material carrying two photographic emulsion colloid layers, each of said layers having a silver halide and a substantially non-mobile colour former dispersed therein, from a colour separation negative, also printing the layer adjoining the base material through the base material from a colour separation reverse negative, and thereafter simultaneously developing the latent images and coupling with the same colour developer,

As applied to three-colour photographlthe process of the present invention'comprises printing the outer emulsion layer of a photographic material comprising a transparent base material carrying two photographic emulsion colloid layers, each of said layers having a silver halide and a substantially non-mobile colour former dispersed therein, from a colour separation negative, coating said printed emulsionlayer withan emulsion composition having a silverhalide and a third substantially non-mobile colour former dispersed therein, printingthe applied emulsion layer from a second colour separation negative, also printing the emulsion layer adjoining the base material through the base material from a colour separation reverse negative, and thereafter simultaneously developing the successively produced latent images and coupling with the same colour developer to produce the three colour record images.

The present invention also provides a photo graphic material for use in the said process which comprises a transparent base. material carrying two silver halide emulsion layers each containing a substantially non-mobile colour former dispersed therein, the colour former. in oneemulsion layer being different from thatin the other andthe two colour formers being such that upon development of the latent images produced on printing the emulsion layer and coupling with the same colour developer, distinct colour record images are produced.

The process is essentially similar to that of the parent application the difierences being that since a material carrying two emulsion layers can be separately produced and used as starting material, the processing in the colour processing laboratory, as distinguished from that involved in the manufacture of the starting material, is reduced and there is greater flexibility in the work to be carried out in the colour processing laboratory. This provides useful advantages and economies in practice.

The present process can be used whether two. three or more colour record images are to be produced.

As in the case of the parent application the colour formers which are present in the emulsion layers are so chosen that they can all be developed with the same colour developer to give the desired colour images. Since all the images are developed simultaneously it follows that, in general, any desired order of printing the images may be adopted since such considerations as desensitization and degradation of an already formed colour image do not arise in the present process. 7 7

The colour formers used according tothe pres:

out invention should be substantially non-mobile. Several methods have been developed in recent years for rendering colour formers substantially non-mobile, the principal ones being the introduction into the molecule of the colour former of one or more groups which impart substantive properties with respect to the photographic emulsion colloid employed and the chemical and/or physical association oi the colour former with some other relatively large molecule which increases the eifective size of the molecules and so substantially reduces their mobility. Thus there may be used colour formers containing alkyl substituents having at least five and preferably from twelve to eighteen carbon atoms and at least one solubilizing group such as carboxylic or sulphonic group in the molecule: or the colour former may be associated with a suitable residue which is dispersed throughout the binder of the emulsion such as that of a high molecular weight waterpermeable but water-insoluble natural resin such as gum mastic, gum dammar, gum sandarach or gumelemi or water-permeable but water-insoluble synthetic resin such as polystyrene, pclymethyl methacrylate, polyvinyl acetate or a cournarona indene resin: or the colour former may have been combined chemically with the residue of a sterol, that of a Substance of the cyclic methane series, that of a polypeptide, that of a highly polymeric carboxylic acid, that of a polymeric material of which a carboxylic acid is a component or that of a carbohydrate.

The emulsion layers are conveniently gelatine emulsions or normal characteristics and preferably are emulsions of reduced gelatine silver ratio (based on the silver nitrate used in their production) of not more than 1.5 to land most pretera'bly' of approximately 1:1. As pointed out in British Patent No. 585,477 more satisfactory adhe'sion between the emulsion layers as well as a voldance of reticulation and frilling in the processing of a multilayer material is secured by the'use of these ratios. The use of emulsion layers having these colloid/silver ratios is of a special value when one or more additional emulsion layers are coated upon the material as happens in the processing when three or more than three colour record images are to be produced. Mora over, the use of such emulsions enables the colour images to be accommodated within a minimum of depth.

When the present process is used for the production of a two-colour image the starting materials required include the photographic material comprising a transparent base carrying two colloid emulsion layers each containing silver halide and a substantially non-mobile colour former, a colour record separation negative and a colour record reverse separation negative. It will be understood that the emulsions are preferably the gelatine emulsions of reduced gelatine silver ratio referred to above. The colour formers, which are chosen having regard to the final positive colour records to be produced, may for example be yellowish-red and cyano colour formers. A yellowish-red colour former suitable for incorporation in a gelatine emulsion is l-('-sulpho-3-stearylamino-phenyl) -3-methyl-5-pyrazolone. Suitable cyan colour formers for gelatine emulsions are di- (2,8 dihydroxy 3 naphthoic acid) benzidide, naphthalene 1 hydroxy 2 stearylcarbonamido-4-sulphonic acid, naphthalene-l hydroxy- 2 N (dodecylcarbonamido) 4 sulphonic acid, naphthalene l hydroxy 2 (2' methyl stearylamino-5-sulphophenyl) -carbonamide and naphthalene l hydroxy 2 carbon (N stearyl-lNeisophthalyl) amide. There is also preferably incorporated into each of the emulsion layers a fugitive yellow dyestufi such as tartrazine, acraflavine or photophor basic yellow which prevents undue penetration of the printing light. The outer emulsion layer of the material is printed in the usual way, from the colour record separation negative and the layer adjacent the base material is printed, in register, through the transparent base material from the colour record reverse separation negative. Any convenient order of printing the two latent images may be used. The printing may also be done using ultraviolet light irrespective of whether a fugitive dyestufi is present or not. When, however, the materials present in the emulsion layers sufficiently absorb the incident light to prevent undue'penetration thereof the incorporation of a fugitive dyestuff or the use of ultra-violet light in printing may be unnecessary.

The images having been printed as described above they are simultaneously developed. Development may be carried out directly in which case all the images may be developed, for example, in a bath containing paradiethyl-aminoaniline as colour developer. Other paradialkyl aminoanilines may be used. The development bath is preferably kept in a state of thorough agitation but free from aeration throughout the development.

It is preferred, however, to develop first with a conventional metol-hydroquinone or amidol developer. This development is controlled so as to prevent development being carried too far in view of the intention to subsequently redevelop. The developed material is then treated with a bath containing potassium ferricyanide and potassium bromide to reconvert the developed material to silver bromide. The image is then reexposed and developed again in the colour developer. By proceeding in this way much better control of the formation of the colour images and great consistency has been found to be possible.

When the present process is to be used for the production of a three-colour photographic image the first and second latent images may be produced from a colour separation negative and a colour separation reverse negative in the man ner already described for a two-colour image but it will be understood that the colour formers must then be chosen to meet the requirements for three colour work. Examples of suitable yellow colour formers are terephthalolyl bis-acetanilide, benzoyl acetanilide, 5-(4-stearylamidobenzoylacetamido) isophthalic acid and 4-methoxy benzoylacet N-(2'-methylstearylamino-4'-carboxyphenyl) amide, while examples of suitable magenta colour formers are l-(4'-stearylaminophenyl)-3-methyl-5-pyrazolone, l- (4' phenoxy- 3'-sulphophenyl) -3-heptadecyl-5-pyrazolone, 1-

3'-sulphophenyl 3 (4 -stearylamido-phenyl) 5-pyrazolone and 4-(e-stearyl-e-carboxyproprionamido) -benzoylacetonitrile. The above named cyan colour formers may also be used. Any selected pair of different colour formers may be present in the two emulsion layer starting material and the appropriate colour separation neg ative and positive are used in the printing steps. The outer emulsion layer containing the latent image printed from the colour separation negative is then coated with an emulsion composition containing. a silver halide and a substantially non-mobile colour former. The colour former is so chosen that on developing and coupling with the same coupler as that to be employed for the first and second images the desiredpositive colour record is obtained. Thus if yellow and magenta colour formers are present in the two emulsion layers of the starting material that now used will be the cyan colour former and so on. It is preferred that the applied emulsion composition have a gelatine/silver ratio (based on the silver nitrate used in its production) of not more than 1.521 and conventiently the ratio may be about 1:1. This improves the adhesion between the freshly applied emulsion and the emulsions already carried by the basematerial. The layer is preferably coated at such a thickness as to produce, on drying, a substantially normal coat ing weight of silver halide i. e. one containing from 40 to 80 milligrams, and preferably 50-50 milligrams of silver per square decimeter of coating. The emulsion may contain a fugitive yellow dyestuif such as tartrazine.

When the applied emulsion layer has been dried a latent image is produced therein by printing, in register, from the appropriate colour separation negative. The three latent images are then simultaneously developed, either directly or by re-exposure and redevelopment as already outlined above in the case of a two colour image.

In practising the present invention a silver halide emulsion may be prepared as follows. A solution containing the following is prepared and brought to 70 C.:

Potassium bromide "gin 165 Potassium iodide gms 5 Gelatine gms 50 Water, (distilled) cc 1700 To this solution there is gradually added a solution of 200 gms. of silver nitrate in 2 litres of distilled water. This solution is also'at about 70 C. and the addition of the second solution tothe first will occupy about minutes. The mixture is stirred and maintained at 70 C. for a further minutes to permit of ripening. At the end of the ripening period the emulsion is cooled as rapidly as possible to 45 C. at which temperature 50 gms. of washed gelatine is added and stirred into theemulsion. When thorough dispersion of the added gelatine has been achieved anhydrous sodium sulphate is added to the emulsion until the silver halides and the gelatine have been precipitated. When the precipitate has settled it is collected, broken up and washed in water until substantially all the soluble potassium bromide has been removed. The

washed material is then redispersed at about 60 3 kgm. After redispersion the emulsion is allowed -1 cc. of a 5% solution of saponin in methyl alcohol.

10 cc. of a 5% aqueous solution of chrome alum.

30-50 cc. of a 5% aqueous solution of the selected colour former obtained by dissolving the colour component in aqueous caustic soda.

The choice of the colour former will depend upon the positive colour record which is to be obtained. To secure uniform dispersion of the colour former it is preferred to use a high'speed mixer. The pH of the emulsion is brought back to that prior to the additions with hydrochloric acid.

To produce the starting material (A in the accompanying flow sheet) for the present invention a transparent base material such as a nitrocellulose or cellulose acetate is taken. This is first coated with a primer and then with a silver halide emulsion containing the selected colour former e. g. the yellow colour former which is to be printed through the base when a threecolour image is to be produced. A small addition of tartrazine or other fugitive yellow dye stuff is preferably made at a suitable stage in the production. The emulsion is coated in such an amount as to produce on drying an emulsion layer containing a substantially normal coating weight of silver halide i. e. from 40-80 milligrams I of silver per square decimeter, preferably 50-60 milligrams per square decimeter. After drying the emulsion is coated with a second emulsion which preferably has been prepared in a similar manner to the first emulsion but contains a colour former from which an appropriately coloured image can be obtained when coupled with the same coupler as the first colour e. g. the magenta colour former. The second emulsion may have the same gelatine/silver ratio as the first emulsion or it may diifer therefrom. The second emulsion may also have incorporated therein a fugitive dyestuff, such as tartrazine. Such material having two emulsion layers each containing an appropriate colour former constitutes the essential starting material for the process of the present invention. It will however be understood that the material need not contain the specific colour formers referred to since these willvary depending upon thenumber of colour record images which it is intended to produce. The material is processed as follows:

The outer emulsion layer which contains the magenta colour former is printed from the green record separation negative (B in the flow sheet) and after such printing and either prior to or after printing through the transparent base (C in the-flow sheet) from the blue separation 'reverse negative the outer emulsion is coated with a third emulsion which preferably is similarly prepared to the first and second emulsions but contains a colour former for the remaining colour image which has yet to be obtained i. e. the cyan image colour former, and has a similar gelatine/silver ratio to the other emulsions. This is shown at D in the flow sheet. This emulsion also may have incorporated therein a. fugitive dyestuif, such as tartrazine. Alternatively, it also may be printed using ultra-violet light. When the third emulsion contains the cyan'col our former, it is printed from the red record separation negative (E in the flow sheet). If the innermost emulsion layer has not yet been printed it is then printed through the base from the blue separation reverse negative.

The three layer film containing the three latent images is now ready for development and this may proceed as follows. A bath is. made up containing:

Para-diethylaminoaniline sulphate gms 3 Sodium sulphite gms 2 Potassium carbonate gms Potassium bromide gmsr 2.5

Water to make litre -1 The time. for development using the colour components containing. at least one long aliphatic carbon chain has been found. to be 10-20 minutes depending upon the characteristics of the emulsion layers and the degree of contrast required. The developed images are shown at F in the flow sheet.

After development the film is rinsed in running water for a short time and the metallic. silver images are removed (G in the flow sheet.)- by treating the film in the following bleaching bath:

Potassium ferricyanide "gins" 10 Armenia, 28% cc 10 Water to make litre 1 after which the him is again rinsed and then treated with a strong aqueous solution (about 20%) of sodium thiosulphate (H in the iiow sheet).

As previously indicated, however, it is preferred first to develop all three images to silver in a metolhydr.cquinone developer. This is made as follows:

Metol gms 1.5 Sodium sulphite gms 75 Hydroquinone gms 2.5 Potassium bromide gms 0.5 Water to make litre 1 l he above solution is adjusted to a pH of 10.2 by addition of sodium or potassium carbonate. The film carrying the three latent images is developed in this solution, washed and fixed. The three metallic silver images are then converted to silver bromide by treatment with. the ioliowing bath:

Potassium ferricyanide gms 20 Potassium bromide gms 10 Water to make litre 1 when fully bleached, the film is rinsed and exposed to white light and then the colour images are developed in the para-diethylaminoaniline bath given above, after which. the images are bleached and silver removed with sodium thiosulphate as outlined above.

More than one colour component may be incorporated into any one of the applied emulsions so long as upon colour development an image of the correct hue is obtained. Thus a mixture of 5- 4 -stearylamidobenzoylacetamide) isophthalic acid and imethoXybenzoylacet-N-(2'-methylstearylaminol' -carboxyphenyl) amide may be used together as the colour components for the yellow image when the developer is a paradialkylaminoaniline such as paradiethylaminoaniline. When more than'three emulsion layers are to be employed the additional layers are added and printed in exactly the same manner as described above for the third layer. Before an emulsion layer is coated the image must be printed therein. It is only the layer adjoining the base, which is printedv through the base from the colour separation reverse negative, which. may be printed at any convenient stage in the process. All the layers which are to be printed from colour separation negatives must be printed before being coated."

When only two colour images are to be produced the processing is carried out in exactly the same way as has just been described for a three colour print apart from the fact that the two layer material does not have to be subjected to any coating step or to the printing step associated with the coating step.

Any convenient choice oi colour separation negative or negatives and reverse negative may be employed. The choice will depend largely upon the particular method by which the negative records are. obtained. Thus they may be obtained by recordal of three different components of a beam of light at three separate recording planes, utilizing a bipack-and-one arrangement or using a suitable tripack material. If. a bipack-andone recording system is being used the rear element of the bipack' may be used to provide the reverse negative. Since the rear of the blpack may conveniently record the red the emulsion layer adjacent the. film base may contain the cyano colour former and the outer layer the magenta colour former. The. coated emulsion will. then contain the yellow colour former.

At any stage after the final coating of: the film a protective outer supercoating of emulsion or of a lacquer may be applied to the film to preserve it from damage by abrasion. A gelatine emulsion may be employed or a transparent lacquer having a basis of a film-forming material which will adhere to gelatine, such as a polyvinyl alcohol lacquer.

What we claim is:

1. A process for the production of, a multicoloured photographic image using at least three colour separation. negatives which comprises printing the outer emulsion layer oi a photographic material comprising a base material carrying two photographic emulsion layers, sensitive to the same part of the spectrum and on the same side of the base, each of said layers containing a silver halide and a colour former which.

is substantially non-diffusing under the process conditions dispersed in a photographic emulsion colloid, from a colour separation negative, coating the printed emulsion witha composition containing a silver halide and a colour former of said non-diffusing type but adapted to produce a different colour image dispersed. in the same colloid as that present in said emulsionlayers, printing the resulting emulsion layer from a sec-- ond separation negative, also printing, inthe layer adjoining the base material through the base material using light of substantially the same spectral quality as that used for printing the outer emulsion layer from a third colour separation negative, the colour formers present in the layers being so chosen that upon development with a developer capable of forming dyes coloured images of correct hue are obtained, simultaneously developing the successively produced latent images with a developer capable of forming dyes from said colour formers and removing developed silver from the images.

2. The process according to claim 1 in which the concentration of the ingredients of the coating composition is such as to produce a silver halide emulsion layer having acolloid silver ratio, based on the silver nitrate used in its pro duction, of not more than 1.5 to i.

3. The process according to claim 1 in which the photographic emulsion colloid is gelatine and the colour formers employed contain at leastone long aliphatic chain and at least one solubilizing group in the molecule.

4. The process according to claim 1 in which the colour separation negatives are blue, green and red separation negatives and the colour formers employed are such that upon development with said developer there are produced yellow, magenta and cyan images therefrom.

5. A process for the production of a multicoloured photographic image using at least three colour separation negatives which comprises printing the outer emulsion layer of a photographic material comprising a base material carrying two photographic emulsion layers sensitive to the same part of the spectrum and on the same side of the base, each of said layers containing a silver halide and a colour former, which is substantially non-diffusing under the process conditions dispersed in a photographic emulsion colloid, from a colour separation negative, coating the printed emulsion with a composition containing a silver halide and a colour former of said non-diffusing type but adapted to produce a different colour image dispersed in the same colloid as that present in said emulsion layers, printing the resulting emulsion layer from a second colour separation negative, also printing in the layer adjoining the base material using light of substantially the same spectral quality as that used for printing the outer emulsion layer through the base material from a third colour separation negative, the colour formers present in the layers being so chosen that upon development with a developer capable of forming dyes coloured images of correct hue are obtained, simultaneously developing the successively produced latent images with a developer incapable of forming dyes from said colour formers, removing unused silver halide, reconverting the developed silver images into silver halide, re-exposing and developing with a developer capable of forming dyes from said colour formers and removing developed silver from the images.

6. The process according to claim 5 in which the concentration of the ingredients of the coating composition is such as to produce a silver halide emulsion layer having a colloid silver ratio based on the silver nitrate used in its production of not more than 1.5 to 1.

'7. The process according to claim 5 in which the photographic emulsion colloid is gelatine and the colour formers employed contain at least one long aliphatic chain and at least one solubilising group in the molecule.

8. The process according to claim 5 in which the colour separation negatives are blue, green and red separation negatives and the colour formers employed are such that upon development with the same colour developer there are produced yellow, magenta and cyan dye images therefrom.

JACK HOWARD COOTE. KEITH MILTON HORNSBY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,260,324 Capstaif Mar. 26, 1918 2,153,617 Eggert et al Apr. 11, 1939 2,159,600 Murray et al May 23, 1939 2,186,849 Wilmanns et al Jan. 9, 1940 2,200,018 Bertrand May 7, 1940 2,251,965 Verkinderen Aug. 12, 1941 2,415,626 Coote Feb. 11, 1947 2,443,909 Hanson, Jr., et al. June 22, 1948 FOREIGN PATENTS Number Country Date 520,076 Great Britain Apr. 15, 1940 

